\directlua{
lua.bytecode[1] = function ()
l3kernel = { }
function l3kernel.strcmp (A, B)
if A == B then
tex.write("0")
elseif A < B then
tex.write("-1")
else
tex.write("1")
end
end
end
lua.bytecode[1]()
}
\long\def\pdfstrcmp#1#2{%
\directlua{
l3kernel.strcmp("[[#1]]","[[#2]]")
}%
}
\pdfstrcmp{a}{a}
\bye